The present application claims priority under 35 U.S.C. xc2xa7119 to Korean Patent Application No. 98-20287 filed on Jun. 1, 1998, the entire contents of which are hereby incorporated by reference for all purposes.
The present invention relates to an inspection system for inspecting wafers, and more specifically, to an inspection system for inspecting a wafer sidewall to detect a wafer having a sidewall defect, i.e., a deviation from a desired wafer sidewall. Furthermore, this invention to relates to an inspection method for inspecting a wafer side wall to detect a sidewall defect.
Conventional semiconductor device fabrication may include the deposition and/or formation of various layers such as polycrystalline silicon, silicon dioxide, silicon nitride, and metal layers, etc., over the surface of a silicon substrate. Various processes used include ion implantation, oxidation, photolithography, etching, metallization, and chemical mechanical polishing. Various layers are patterned and formed repeatedly to dispose conductive interconnection patterns between monolithic electronic components such as transistors, capacitors and resistors, and insulating layers; for example, silicon dioxide and phosphosilicate glass.
In the formation of semiconductor devices and structures on the semiconductor wafers using the various processes listed above, the semiconductor wafers pass through various semiconductor device fabrication facilities and processing machinery. According to the characteristics of each process, conditions such as processing temperature and pressure inside the corresponding facility or machine vary. In addition, the silicon wafers are passed through various mounting techniques and apparatuses used to fix the die, e.g., a chuck.
As a result, a sidewall of the wafer is often damaged by heat, pressure, and physical contact during the various processes. Once an initial defect or damage region is created, additional processing steps may propagate the defect or induce damage to the wafer. Stress on the wafer may concentrate pressure on a damaged portion and breakage may occur which will cause contamination of other wafers and components of the fabrication facility or machinery itself.
Accordingly, there is a need for a method and apparatus for inspecting the wafer side wall to detect and ensure that the wafer is acceptable for successful semiconductor processing. Typically, acceptability means that no defect or damage exists to the wafer sidewall.
Common techniques for semiconductor wafer sidewall inspection include manually selecting a number of wafers from a batch of wafers and visually inspecting each wafer side wall to detect any anomalies on the sidewall surface. However, often a visual inspection of the wafer sidewall does not provide adequate detection accuracy. Moreover, the manual inspection process is time consuming, and requires involved operator intervention.
Accordingly, there is a need for a method of quickly inspecting a semiconductor wafer sidewall to detect any defects or damage so that the wafer may be successfully used in the subsequent fabrication of a semiconductor product. There is a need for a method of quickly inspecting the wafer sidewall to detect and remove unacceptable wafers, thereby increasing semiconductor device yields.
In addition, cross contamination of semiconductor wafers by stray particles broken from other wafers needs to be minimized by increasing wafer quality to maintain the reliability of expensive semiconductor fabrication machinery.
Finally, there is a need for minimizing operator dependency in ensuring semiconductor product reliability to maximize semiconductor productivity in semiconductor devices by reducing the semiconductor production on defective wafers.
The present invention is therefore directed to a method and system for inspecting wafer sidewalls which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.
According to an object of the present invention, a method and apparatus automatically inspects a wafer sidewall to determine acceptability of the wafer for use in the subsequent fabrication of a semiconductor product.
Another object of the present invention is to provide a method and system for quickly inspecting the wafer sidewall to detect and remove unacceptable wafers, thereby increasing semiconductor device yields.
Yet another object of the present invention is to minimize cross-contamination of semiconductor wafers by broken wafer particles by reducing wafer breakage to maintain the reliability of expensive semiconductor fabrication machinery.
A further object of the present invention is to minimize subjective operator error in ensuring semiconductor product reliability to further productivity in semiconductor devices by minimizing the processing of defective wafers.
At least one of the above and other objects may be realized by providing an apparatus including an image information acquisition unit, such as a CCD (Charge Coupled Device) camera, having an image sensor which captures image data of the wafer sidewall and an analyzer which compares the measured image data to data from a desired sidewall to determine if the wafer sidewall is acceptable.
The analyzer may be a computer and may include an output unit for providing paper output and/or visual output may be connected to the analyzer for indicating the results of the comparison to a user. If more than one wafer sidewall portion is to be inspected, the requisite data is preferably acquired by one of the two following specific embodiments.
In a first specific embodiment, the inspection system may include a vertical member fixed to a base and a wafer revolver, situated on the base, to rotate the wafer. The wafer sidewall surface is exposed and rotated in front of the image acquisition unit. A horizontal member is attached to the vertical member at one end, and has the image acquisition unit attached to the other end such that the image acquisition unit is positioned over the exposed sidewall surface of the wafer. A stage is disposed on a base which secures the wafer revolver and allows the wafer revolver to move horizontally along a center axis of the wafer to align additional wafers which may be placed in the holder.
In a second specific embodiment, the image acquisition unit may include an illuminator and a detector attached to a moveable attachment head mounted to an end of a horizontal support. The end of the horizontal support in this embodiment has a toothed rack which meshes with a pinion gear inside the moveable attachment head to allow controlled movement of the image acquisition unit along the horizontal support.
At least one of the above and other objects of the present invention may be realized by providing a method for inspecting a wafer including capturing image data of a sidewall region of the wafer and comparing captured data to data for a desired sidewall to determine whether the wafer being inspected is acceptable.
The method may include providing paper output and/or visual output for indicating the results of the comparison to a user. If more than one wafer sidewall portion is to be inspected, the requisite data is preferably acquired by one of the two following specific embodiments.
A method according to the first specific embodiment of the present invention further includes counting the number of wafers as the stage is moved horizontally along the center axis of the wafer to scan the number of wafers present in the cassette. The image data of a first wafer having a first sidewall is captured during a complete rotation of sidewall surface area. After a complete rotation of sidewall surface area, the stage is moved and image data of a second wafer is captured through the complete rotation of the second wafer. This process is repeated until all wafers in a cassette are processed.
A method according to the second specific embodiment of the present invention further includes counting the wafers by moving a moveable attachment head to scan the number of wafers present in the cassette. A detector is moved across the exposed sidewall surface of all the wafers in a cassette to capture a portion of the sidewall image information from all the wafer sidewalls simultaneously. The wafers are then rotated by a first amount and the process repeated until a composite of all the sidewall surface area of all the wafers in the cassette is captured.
These and other objects of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.